The objectives of this investigation are to further develop techniques and instrumentation for the determination of exposure and dosimetric parameters, at 915 mHz and 240 mHz, and the influence of pulsed and continuous exposure, and peak power and average power (pulsed irradiation), and to refine the dosage and monitoring procedures through refinement of techniques and instrumentation for quantitative measurement of modulated and pulsed transmission of 2450 plus or minus mHz and 915 plus or minus 25 mHZ and power ranges at or near those currently considered acceptable and to determine the effects of low dose chronic prenatal microwave irradiation on a) embryonic and fetal development in the rat, b) postnatal deveopment in the rat, c) the reproductive capacity of the rat, and d) the central nervous system of the exposed adult offspring. The procedure will include 3 power ranges at 2 transmissions and 2 frequencies (2450 mHz and 915 mHz) at 4 time periods in the rat pregnancy plus paired controls.